Feeding-pressure regulator for earth-boring bits



Oct. 27, 1925.

.E. SMITH FEEDING PRESSURE REGULATOR FOR EARTH BORING BITS Filed Jan. 2-1, 1925 2 Sheets-Sheet 1 R m mm a w r J f. A M W F SIT r: Z \WVQVZZ /%V 2.. u w 6 0 fllJZ 7 o I nnfiwu 2H 3 3 JMWZ M III- 1 A E5, 5;? 1.1.1 A@ /////fl/ \K 1, x A M 5 W BY 1 S km.. W ATTORNEYS Oct. 27, 1925. 1,558,511

'E. SMITH FEEDING PRESSURE REGULATOR FOR EARTH BORING BITS Filed Jan. 21., 1925 2 Sheets-Sheet 2 v 1 INVENTOR f'aaisrav SM/I/I a1; ATTORNEYS Patented Oct. 27, 1925. UNITED STATES I 1,558,511 PATENT (OFFICE.

EGGLESTON SMITH, OF HAMARONECK, NEW YORK, ASSIGNOB T0 EGGLESTON DRILLING CORPORATION, OF DOVER, DELAWARE, A CORPORATION OF DELAWARE.

FEEDING-PRESSURE REGULATOR FOR EAItTH-BORING BITS.

Application fl-led January 21, 1925.

To all whom it may concern:

Be it known that I, EGGLESTON SMITH, a citizen of the United States, residing at Mamaroneck, in the county of Westchester, State of New York, have invented certain new and useful Improvements in Feeding- Pressure Regulators for Earth-Boring Bits; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to earth-boring such, for example, as in drilling in connection with mining operations or in drilling for oil, water, gas, and the like. ticularly, the object of the invention. 1s the provision of improvements in applymg, regulating, or controlling the feeding pressure of earth-boring bits.

In carrying on drilling operations of this character, it is important, in order to obtain the maximum rate of cutting, to apply the correct drilling or feeding pressure to the bit. The correct feeding pressure to secure maximum cutting speed varies with the different materials or formations encountered by the earth-boring bit. The subject of proper feeding pressure is of especial importance when earth-boringbits constructed of abrasive material, such as carborundum or the like, are employed. I

Among other things the present invention affords a means for applying a feeding pressure, which means is semi-automatic in operation, which is relatively easy to ad ust, which is not liable to stlck or jam, which overcomes the pressure of gas, water or oil from the well, which renders it easy to start the drilling of a hole, and which provides uniform pressure upon the bit at any inclination of drilling. Furthermore, the device is convenient to use and economical to manufacture.

According to the present invention, I utilize fluid pressure for securing the feeding pressure in Whole or in part. The fluid pressure may be supplied from any convenient source but I preferably employ the water which is pumped down the drill pipe for lubricating the bit and carrying away the drillings. However, air or steam may be used, if desired.

In carrying out the invention, a suitable driving means is provided for rotating the More par- Serial No. 3,711.

bit, this means including an appropriate device for permitting longitudinal movement of the drilling bit with respect to the driving means, one of the purposes of which is to allow the bit. which is operatively associated with the driven member, to advance or feed automatically as the hole is cut. This device ordinarily includes a driving member and a driven member so associated together that the rotational movement of the driving means which is connected to the driven member is imparted to the driving member, but allowing the driven member to slide longitudinally wlth respect to the driving member. With such a device, means operable by fluid pressure is associated in such a manner as to exert a feeding pressure upon the-driven member by which the pressure is imparted to the drilling bit.

The feeding pressure device just mentioned, which is operable by a fluid pressure, preferably comprises a cylinder having a piston movable therein under the action of the fluid pressure. Elastic means, such as a spring, is so associated with the cylinder and piston as to oppose the movement of the piston under the operating fluid pressure and transmit this pressure to the cylinder. With these parts arranged in operative position, the fluid pressure, such for example as the drilling liquid, exerts a force upon the piston; compresses the spring or other elastic means and thereby exerts a yielding longitudinal pressureupon the cylinder, which pressure is transmitted to the drilling bit through the above mentioned driven member. The fluid pressure applied to the piston may be controlled from the surface of the ground so as to vary the feeding pressure applied to the bit, but preferably means are provided within the feeding pressure device for limiting the magnitude of the pressure coming from the fluid which can be transmitted to the bit.

This means preferably. comprises a channel suitably arranged to bypass-the fluid. from the top of the piston when the piston has moved forward and compressed the elastic means a predetermined amount. Thus, as soon as the piston opens the bypass the pressure of the fluid is relieved and the feeding pressure exerted on the drilling bitis thereby positively limited. The fluid which is bypassed from the cylinder is preferably arranged to travel around the pislilt) ton and forward or downward to serve as drilling fluid for the bit.

The feeding pressure device of the mven- I tion may be utilized both with apparatus Illfor drilling deep wells and with apparatus for drilling comparatively shallow holes, such as in mining work. For the former purpose, the feeding pressure device 1s constructed in the form of a completely selfcontained unit which is particularly adapted to be lowered down thedrill pipe of a. rotary drillin rig by means of a cable. When thus Iowered into the drill pipe, the device is brought into operative position in coaction with the upper end of the driven member.

Such a feeding pressure device is semiautomatic in its operation for the reason that, although it does not vary the feeding pressure when the drilling bit encounters formations of different hardness, nevertheless it does automatically effectively limit the feeding pressure whici can be applied t0 the bit.

In my prior applications for Letters Patent of the United States, Serial No. 637,- 761, filed May 9, 1923; Serial No. 681,032, filed December 17, 1923, and Serial No. 712,197, filed May 10, 1921, I have shown and described several methods and apparatus for operating rotary earth-boring bits, particularly abrasive bits both with reciprocating and with rotary drilling rigs. In these prior applications means are provided for operating the drilling bits under such conditions of feeding pressure control as to make the abrasive bit extremely advantageous to use.

All of these prior devices include a driving means and driving and driven members, which members are longitudinally movable with respect to one another. The feeding pressure is supplied by gravity or by means of a spring, and although these prior devices have been found to be operative and successful, my more recent investigations have resulted in the present improvements in the application of the feeding ressure.

In using the drilling apparatus isclosed in these prior applications, the maximum feeding pressure which is ap lied to the drilling bit is determined by t e weight of the bit itself and a portion of the apparatus which is'connected thereto, namely, the driven member. In order to increase or decrease the amount of this maximum feeding pressure, it is necessary to increase or decrease the weight of these parts. This may be done, for example, by adding a weight to the to of the driven member or by inserting a ollow sinker between the ,driven member and the bit.

When a weight is added at the top of the driven member, the friction with-the walls of the drill pipe is increased and there is a ing of a hole, a formation of particularly hard rock is encountered, it is necessary to increase the feedlng pressure and the en- 'tire drilling apparatus must be withdrawn from the hole in order to insert the section or sections of additional weight. This requires a considerable amount of time, par- 1 ticularly when a rotary drilling rig is employed, inasmuch as the drill pipe must be removed from the hole section by section. Again, when starting the drilling of a hole, it may be difficult, on account of the limitation in the height of the derrick, to add sufficient weight to secure the proper feeding pressure.

\Vhen operating with the feeding pressure device of the present invention, however, and the drilling bit strikes a particularly hard formation, it is only necessary to hoist the feeding pressure device up to the surface of the ground by means of a cable and then adjust it to secure a greater feeding pressure. This can readily be done, for example, by changing to a heavier spring or by placing washers under the lower end of the spring.

The invention will be better understood by referringto the accompanying drawings which illustrate by way of example two embodiments of the invention. In these drawings:

Fig. 1 is a longitudinal section of the lower end of a drill pipe provided with a slidable joint having driving and driven members and associated with which is the feeding pressure device of the invention. In this view the piston has been moved forward to compress the spring and open the bypass.

Fig. 2 is a longitudinal section of the feeding pressure device removed from the well and showing the piston in released position.

Fig. 3 is a transverse section on line 33 of Fig. 1.

Fig. 4 is a transverse section on line 44 of Fig. 1.

Fig. 5 is a transverse section on line 5-5 of Fig. 2.

Fig. 6 is a longitudinal section of a modification of the invention as applied to a drilling machine for use in drilling horizontal holes. This View is more or less diagrammatic in character.

Fig. 7 is a transverse section taken on line7-7 of Fig. 6.

Referring now to the accompanying drawings, and particularly Figures 1 to 5 inclusive, the drill stem or drive pipe 10 is secured at its lower end by meansof a collar'll, to a slidable joint or coupling comprising adriving member 12 and a driven member 13'... The driven member 13 is generally Circular in cross-section and slides or telescopes through a circular aperture 14 in the driving member. Positive rotational movement is imparted, however, from driving member 12 to driven member 13 by means of oppositely disposed, keys or splines 15 which coact with corresponding slots 16 in thedriving In-ember.

The lower end of drivenmember 13 is appropriately threaded to receive a' drilling bit 17. Any form of bitpmay be employed but I prefer to use a bit made of abrasive material and comprising, for example, a body 18 of carborundum which is secured in the bit mounting 19 in any suitable manner, such for example as by means of a lead binder 20.

The upper end of driven member 13 has an enlarged head 21 which coacts with the top of driven member 12 when the slidable coupling is in extended position to prevent the two members from separating. A longitudinal bore 22 extends throughout the length of driven member 13 for the purpose of conveying drilling fluid to the abrasive bit and for providing a space for the reception of a core when, as in the example shown, a core cutting bit is employed.

The feedingpressure device of the invention comprises a cylinder 23 adapted to be lowered by means of a bail 24 and a cable 25 into the drill pipe 10 and rest upon the head 21 of driven member 13. In order to facilitate the engagement of the feeding pressure'device with the member 13 when the feeding pressure device is lowered into operating position, the cylinder 23 is provided with an extension 26 of reduced diameter which is adapted to fit within the 21 to facilitate the entrance of extension 26 therein and to provide a relatively tight seat with a conical surface 28 upon the cylinder 23 for a purpose which will hereinafter appear.

Within cylinder 23 there is mounted a slidable piston 29 which is secured to a piston rod 30 by means of nuts 31. On the opposite end of the rod 30 there is secured a guide 32 which slides in a passage-way 33 provided in extension 26. By this construction piston 29 is caused to be freely slidable within cylinder 23. A contraction 33 in the passageway 33 provides a shoulder which acts as a stop for the guide 32. thereby holding piston 29, guide 32 and a by ton 29 moves downwardly spring 34 is compressed a ainst shoulder 35. Appropriately positioned in the walls of cylinder 23 is pass channel 36, the upper end of which is a apted to be opened by the movement of piston 29 after spring 34 has been compressed a predetermined amount. In Figure 2 the piston is shown above the end of byp'a'ss 36, the spring 34 being in extended position, whereas in Figure l the piston has moved down and opened the bypass.

.lVhen this apparatus is placed in operation, the drill pipe 10 is lowered down the hole until bit 17 strikes the bottom of the hole and the slidable coupling is moved to retract the head 21 above the top of driving member 12. The feeding pressure apparatus is then lowered down 'the drill pipe by means of cable 25 into the position shown in Figure 1. The drill pipe 10 is now rotated which causes, through the slidable joint, the rotation of bit17.

Drilling liquid under appropriate pressure is now supplied through drill pipe 10 and because of the close fit which is made by the cone surface 28 with the flaring opening .27

the liquid is confined within the interior of cylinder 21 and forces piston 29 downward against the action of spring 34. This downward movement continues until the piston reaches the position shown in Fig. 1 in which bypass 36 is opened. The drilling liquid can then pass downwardly through bypass 36 and into the passage-way 33, thence through the plurality of channels 37 which are provided in guide 32 for this purpose. Emerging from these channels, the liquid passes through bore 22 downwardly to the cutting surface of the drilling bit.

Before the application of the drilling liquid, the feeding pressure upon the bit is provided only by the weight of driven member 15 and the cylinder 23. This may or may not be sufficient to cause the effective operation of the bit, depending upon the design of these parts. hen, however, piston 29 is. moved downwardly under the action of the drilling fluid the compression of spring 34 transmits this pressure to the cylinder 23 by which it is transmitted to the bit 17. Thus by choosing a spring 34 of appropriate di mensions any desired feeding pressure upon the bit may be obtained Referring now to Figures 6 and 7 of the accompanying drawings. the drilling machine here shown comprises a frame 38 which may be mounted upon any appropriate support 39 and within this frame arecarried members which correspond to the parts described above. The driving member comprises a longitudinally extending quill which rotates preferably in ball thrust bearings appropriately mounted in frame 38. Quill 40 is mounted at the rear end with a gear 42 meshing with a pinion 43 mounted on the shaft of a driving motor 44. Quill 40 has a longitudinal opening extending from end to end and in the forward end of this opening there is mounted a driven member 45 which is slidable longitudinally and which is provided with keys 46 similar to keys 15 of Figure 1. Driven member 45 is thus positively rotated by quill 40 and at the same time is slidable longitudinally therein. Upon its forward I end driven member 45 carries a bit 47, preferably of abrasive material. An intermediate section of drill stem 48 may be interposed between driven member 45 and the bit, if desired, as is shown in Figure 6.

Driven member 45 extends through to the rear of the drilling machine and has a cylindrical bore 49 extending from end to end thereof. A piston 50 is mounted within this bore upon a piston rod 51 as before. This rod is, however, slidable within a guide 52 which is perinanentlyfixed in position with 'in bore 49 but provided with a plurality of water channels 53. Guide 52 acts as a stopagainst which a spiral spring 54 presses under the movement of piston 50,.th1s spring being mounted upon the piston rod 51.

i The interior 0 quill 40 is chambered out at 55 to a diameter somewhat larger than the driven member 45 to allow for the passage of drilling fluid around the piston and to afford means for limiting the longitudinal movement of driven member 45. For this latter purpose a sleeve 56 is rigidly mounted on the exterior ofdriven member 45. I The forward and rear ends of this sleeve form shoulders adapted to coact with the end walls of chamber 55 to stop the movement of member 45 in both directions.

; Drilling fluid is applied at the right hand end of the machine and passes through bore 49 to the piston. The pressure of this fluid moves the piston forward to compress the spring and in Figure 6 the piston is shown in the forward position where it has opened a pair of ports 57 allowing the fluid to escape into chamber 55. From this chamber the fluid passes through a second pair of ports 51 back into the bore 49 below the piston 50. The liquid then passes onwardly through channels 53 and thence forward to lubricate the bit.

In this apparatus the feeding pressure is controlled by means of spring 54 and regardless of the pressure of the drilling fluid used, it is impossible for the machine operator to apply more than the predetermined feeding pressure to the drilling bit. the feeding pressure thus bein automatically limited. When drilling a horizontal hole with this appara tus, the weight of the moving parts does not affect the feeding pressure applied to the bit and this pressure is exerted entirely by the. compression of spring 54 under the influence of the fluid pressure a plied to piston 50. In other werds, the feeding pressure is applied entirely by the fluid pressure regulating device. During the drillin of holes which are inclined either upwardIy or downwardly with respect to the horizontal, the weight of the moving parts, of course, tends to add to or' subtract from the feeding pressure applied by the fluid pressure regulator, but the weight of these moving parts is comparatively small and. even when drilling vertical holes, has a negligible effect upon the feeding pressure exerted by the fluid pressure device. Hence, the feeding pressure is substantially uniform at all inclinations of drilling.

In drilling deep wells with the drilling apparatus illustrated in Fi res 1 to 5 inclusive, the ease with which the feeding pressure regulator of the invention can be adjusted to meet various conditions of drillingis an important advantage. For example, if the drilling bit passes through a relatively soft formation to a relatively hard ro1k, it will probably be desirable to increase the feeding pressure applied to the bit in order to cut through the harder mate rial at a maximum rate of speed. In order to make the adjustment for this increased feeding pressure, it is only necessary to hoist the removable feeding pressure regulator shown in Figure 2 to the surface of the ground by means of-the cable 25 and then either insert a larger spring 34 or place washers upon shoulder 35 in order to cause a greater compression in spring 34 before piston 29 opens the bypass 36. This 0 eration of hoisting and adjusting is not only practicable but is convenient from the drillers point of view.

An additional advantage of the present feeding pressure regulator is the reduction or elimination of any tendency that may exist in the slidable coupling to stick or jam. This tendency is overcome because of the application of a positive and controllable fluid pressure for producing the pressure upon the bit.

In the drilling of wells for oil, water or gas, it not infrequently happens that these elements are encountered in the earth under such pressure as to seriously interfere with the drilling o erations. However, when employing the ceding pressure apparatus of the invention, this pressure is overcome by the pressure of the drilling fluid, and inasmuch as the feeding pressure exerted upon the drilling bit depends upon the difference in pressure between th opposit sides of the piston, the feeding pressure will not be lessened by the pressure of oil, water or gas which tend to flow up the hole being drilled.

The feeding pressure regulator of the invention provides a convenient and efficient means for obtainin the required feeding pressure in the starting of a hole because the regulator has -a relatively small diameter, is light in weight and can be readily manipulated by a derrick. The employment of long sections of a sinker or other weight in order to secure the appropriate feeding pressure is thence avoided.

A further advantage which is not to be overlooked resides in the economy of manufacturing. The slidable joint, the members ofwhich are connected by straight longitudinal keys, is capable of being made easily and cheaply, the principal process consisting of drawing the material through suitable dies which can be done at the steel mill. The machining of the slidable joint is thereby limited to the cutting of the threads at both ends. The parts of the fluid pressure regulator are few in; number and of simple form. They can all be made by simple casting, forging and machining operations. p

I claim:

1. In an earth-boring apparatus the combination of an earth-boring bit, a driving element extending down the hole being drilled for rotating the bit, a device for connecting the bit to the lower endof the driving element for imparting ositive rotation tothe bit and for permittmg longitudinal movement, thereof with respect to the driving element, and means operable by fluid pressure and associated with said device for exerting a feeding' 'pressure upon the bit.

2. In an earth-boring apparatus the combination of an earth-boring bit, a driving element extending down the hole being drilled for rotating the bit, a device for connecting the bitto the lower end of the driving element for imparting positive rotation to the bit and. for permitting longitudinal movement thereof with respect to the driving element, said device including driving and driven members, and means operable by fluid pressure and associated with the driven member for exerting a feeding pressure upon the bit.

3. A feeding pressure device for earthboring bits comprising, a' cylinder adapted to receive fluid pressure, a bit operatively connected thereto, a. piston movable therein,

' and elastice means for opposing said movement and for transmitting to the cylinder pressure applied to the piston.

4. A feeding pressure device for earthboring bits comprising, a cylinder, a bit operatively connected thereto, a piston movable therein under the influence of fluid pressure, and elastic means associated with the piston and cylinder for transmitting by the compression of said elastic means a ongitudinally acting force to the cylinder.

able therein under the action 0 fluid pressure, elastic means for opposing said movement and for transmitting to the cylinder pressure applied to the piston, and means for stopping the movement of the piston when t e pressure applied thereby'to the cylinder reaches a predetermined amount.

7. A feeding pressure device for earthboring bits comprising, a cylinder, a bit operatively connected thereto, a piston movable therein under the action of fluid pressure, elastic'means for transmitting by the compression thereof a lon 'tudinally acting force to the cylinder, an means for stopping the movement" of the piston when the compression in the elastic means reaches a predetermined amount.

8. A feeding pressure device for earthboring' bits comprising, a cylinder, a bit operatively connected thereto, means for supplying fluid pressure thereto, a piston movable in the cylinder under the action of said pressure, elastic means for transmitting by the compression thereof a longitudinally acting force to the cylinder, and means for relieving said fluid pressure when the longitudinally acting force reaches a predetermined amount.

9. A feeding pressure device for earthboring bits comprising, a cylinder, a bit operatively connected thereto, means for supplying fluid pressure thereto, a piston movable in the cylinder under the action of said pressure, elastic means for transmitting by the compression thereof a longitudinally acting force to the c linder, and means un-' der the control of the piston for relieving said fluid pressure when the lon 'tudinally acting force reaches a pre iatermined amount.

10. A feeding pressure device for earthboring bits comprising, a cylinder, a bit operatively connected thereto, means for supplying fluid pressure thereto, a iston movable 1n the cylinder under the actlon'of said pressure, elastic means for transmitting by the compression thereof a longitudinally acting force to the cylinder, the c linder having a by-pass associated therewlth for relieving said fluid pressure and adapted to be uncovered by the movement of the piston when the longitudinally acting force reaches a predetermined amount.

longitudinally acting device for earth- 11. A feeding pressure a cylinder, a bit boring bits comprising, operatively connected thereto, means for supplying fluid pressure thereto, a iston movable in the cylinder under the action at said ressure, a spring coacting with the cylin er and piston to oppose said movement and for transmitting to the cylinder by the compression of the spring pressure applied to the piston, and means for relieving said fluid pressure when the force applied to the cylinder by the pistonreaches a predetermined amount.

12. A feeding pressure boring bits comprising, a cylinder, a bit operatively connected thereto, means for supplying fiuid pressure thereto, a piston movable in the cylinder under the action of said pressure, a spring coacting with the cylinder and piston to oppose said movement and for transmitting to the cylinder by the compression of the spring pressure applied to the piston, and means under the control of the piston for relievingsaid fluid ressure when the force applied to the cyldevice for earthinder by the piston reaches a predetermined amount.

13. Iii an earth-boring apparatus the combination of an earth-boring bit, driving means therefor, means for supply ng drilling liquid to the bit under appro riatepressure, and a feeding pressure ev1ce ass0- cia ed with the bit comprising, a cylinder, a piston movable therein under the pressure of the drilling liquid, elastic means for transmitting by the compression thereof a force to the cylinder, and means for relieving the pressure of .the drilling liquid when the longitudinally acting force reaches a predeterm ned amount.

14. In an earth-boring apparatus the combination of an earth-boring bit, driv ng means therefor, means for supply ng drilling liquid to the bit under appropr ate pressure, and a feeding pressure dev1ce associated with the bit comprising, a cylinder, a piston movable, therein under the pressure of the drilling liquid, elastic means for transmitting by the compression thereof a longitudinally acting force to the cylinder, and means under the control of the p ston for relievingthe pressure of the drilling liquid when the longitudinally acting force reaches a predetermined amount.

'15. In an earth-borin apparatus the combination of an earthboring bit, driving means therefor, means for supplying drilling liquid to the bit under appropriate pressure, and a feeding pressure device associated with the bit comprising, a cylinder, a piston movable therein under the pressure of the drilling liquid, a spring coacting with the cylinder and piston to opposite said movement and for transmitting to the cylinder bythe compresthe cylinder pressure applied to the piston. 17. In an earth-borin apparatus the com bination .of an earthoring bit, driving means therefor, and a feedingpressure device associated therewith comprising, a cylinder adapted to receive fluid pressure, a piston movable therein under the action of sad pressure, elastic means for transmitting by the compression thereof a longitudinally acting force to the cylinder, and means for relieving said fluid pressure when the longitudinal acting force reaches a predetermined amount.

18. In an earth-boring apparatus the combination of an earth-boring bit, driving means therefor, and a feeding pressure device associated therewith comprlsing, 0. cylinder ada ted to receive fluid pressure, apiston mova le therein under the action of said pressure, elastic means for transmitting by the compression thereof a longitudinally acting force "10 the cylinder, and means under the control of the piston for relieving said fluid pressure when the longitudinally acting force reaches a predetermined amount.

19. ,In an earth-borin apparatus the combination of an earthoring bit, driving means therefor, and a feeding pressure device associated therewith comprising, a cylinder ada ted to receive fluid pressure, a piston mova 1e therein under the action of said pressure, a spring coacting with the cylinder and piston to oppose said movement and for transmitting to the cylinder by the compression of the spring pressure applied to the piston, and means for relieving said fluid ressure when the force applied to the cyl-- er by the piston reaches a predetermined amount.

20. In an earth-borin apparatus the combination of an earthoring bit, driving means for rotating the bit including driving and driven members movable longitudinally relativeto one another, and a feeding pressure device associated with the driven member comprising, a cylinder adapted to receive fluid pressure, a piston movable therein under the action of said pressure, and elastic means for opposing said movement and for transmitting to the cylinder pressure applied to the piston.

21. In an earth-boring apparatus the combination of an earth-boring bit, driving means for rotating the bit including driving and driven members movable longitudinally relative to one another, and a feeding pressure device associated with the driven member comprising, a cylinder adapted to receive fluid pressure, a piston movable therein under the action of said pressure, elastic means for transmitting by the compression thereof a longitudinally acting force to the cylinder, and means for relieving said fluid pressure when the longitudinally acting force reaches a predetermined amount.

22. In an earth-boring apparatus the combination of an earth-boring bit, driving means for. rotating the bit including driving and driven members movable longitudinally relative to'one another, and a feeding pressure device associated with the driven member comprising, a cylinder adapted to receive fluid pressure, a piston movable therein under the action of said pressure, elastic means for transmitting by the compression thereof a longitudinally acting force to the cylinder, and means under the control of the piston for relieving said fluid pressure when the longitudinally acting force reaches a predetermined amount.

23. In an earth-boring apparatus the combination of an earth-boring bit, driving means for rotating the bit including driving and driven members movable longitudinally relative to one another, and a feeding pressure device associated with the driven member compr1sing,a cylinder adapted to receive fluid pressure, a piston movable "therein under the action of said pressure, a spring coacting with the cylinder and piston to oppose said movement and for transmitting to the cylinder by the compression of the spring. pressure applied to the piston, and means for relieving said fluid pressure when the force applied to the cylinder by the piston reaches a predetermined amount.

24. In an earth-boring apparatus, the com-' bination of a drill pipe provided with a slidable connection having driving and driven members, a drilling bit operatively connected to the driven member and a feeding pressure device operable by fluid pressure and ed to the bit and provided with a seat at its upper end, and a removable feeding pressure device adapted to engage said seat and thereby coact with the driven member.

26. In an earth-boring apparatus, the combination of an earth-boring bit, a drillstem therefor, a slidable connection therebetween having a driven member operatively connected to the bit, said member having a passageway therethrough, and a feeding pressure device operable by fluid pressure and asso'-' ciated with said driven member, said device being provided with a bypass connecting with the passage-way in the driven member so as to supply drilling fluid to the bit.

27. In an earth-boring apparatus, the combination ofa drill pipe provided with a slidable connection having driving and driven members, a. drilling bit operatively connected to the driven member, and a feeding pressure device capable of being lowered through the drill pipe into operative position with respect to the driven member. 7

28. In an earth-boring apparatus, the combination of a drill pipe provided with a slidable connection having driving and driven members, a. drilling bit operatively connected to the driven member and a feeding pressure device capable. of being lowered through the drill pipe comprising a cylinder adapted to rest upon the driven member when in operative position, a. piston movable in the cyl' inder under the pressure of the drilling liquid, elastic means for transmitting said liquid pressure by the compression of said elastic means to the cylinder and thereby to the drilling bit, and means for relieving the pressure of the drilling liquid when the pressure upon the bit reaches a predetermined amount.

In testimony whereof I afiix my signature. 

